Abrasive dressing is a working process of shaping of the grinding tool via trimming or removing the dull surface of the grinding tool in order to restore the grinding performance of the working face and correct the geometrical shape. The effects of abrasive dressing mainly include two aspects: (1) to ensure that the grinding tool obtain the geometrical shape (also called truing); (2) to ensure that the abrasive grains on the surface of the grinding tool could have a certain exposure height (also known as sharpening). Dressing of the grinding tool in a timely and correct way is an indispensable procedure to improve the grinding efficiency and guarantee the grinding quality. For ordinary abrasive tools, diamond tools such as single-point diamond dresser and diamond wheel are used to complete the process of truing as well as sharpening simultaneously.
Super abrasive tools are grinding tools of which super-hard abrasive (diamond and cubic boron carbide) are bonded by different kinds of bond. For super abrasive tools, since abrasive grains are of high hardness and the effective working layer is limited, truing and sharpening is done separately during abrasive dressing. Dressing of super abrasive tools is the key to ensure the normal use, which therefore has always been a hot research topic in this field.
At present, dressing of super abrasive tools includes the following two categories: (1) mechanical removal such as diamond dressing, wheel grinding, free-abrasive lapping, crush dressing, soft-elastic dressing, etc. to remove the bond and abrasive grains of super abrasive products via mechanical action between dressing tools and abrasive tools essentially; (2) dressing using other kinds of energy such as laser dressing which employing light energy to melt and remove the bond, EDM dressing which employing electro spark erosion to remove the bond, ultrasonic vibration dressing which employing ultrasonic energy to remove the bond, or new dressing method combining two methods described above. These kinds of dressing methods play good effect on ordinary super abrasive tools. However, there are still a lot of problems for above methods to be used in precision and ultra-precision grinding typed super abrasive tools.
Comparing with ordinary super abrasive tools, precision and ultra-precision grinding typed super abrasive tools is characterized by the use of fine grains with mostly micron or sub-micron scale, which bring a great challenge to dressing process. For the conventional mechanical removal method, it is difficult to control the removal amount of the bond in micron or sub-micron scale. So energy typed dressing methods are mainly used in fine grain super abrasive tools, including the following: spray sharpening, laser sharpening, MAP sharpening, ELID sharpening, etc. However, each method has a corresponding shortage: strict safety protection is necessary for spray sharpening; laser source using in laser sharpening is expensive, and also laser damage to diamond abrasive occur easily; MAP sharpening applies only to low rigidity abrasive tools; ELID sharpening requires a special DC supply unit which is expensive, and the current supply is unstable because of the wear of the brushes in the sharpening device, which affects the sharpening effect of the grinding wheel.
In order to achieve ideal dressing effect of fine grain super abrasive tools, a reasonable amount of bond removal must be guaranteed. If the removal amount is too large, abrasive grains are easy to fall off because of lacking holding force; if the removal amount is too small, it is difficult to achieve the dressing result because of not enough exposure height of grains and chip space. The removal amount controlling of ultra-precision grinding typed super abrasive tools is much more difficult since the size of grain is smaller, and therefore dressing of this type of abrasive tools is harder than ordinary abrasive tools. It is urgent to develop a novel dressing method which is cost-effective, energy-saving, environmental-friendly and suitable for ultra-precision grinding typed super abrasive tools.